Dual cure coating compositions

Abstract

Dual cure coating compositions are prepared by one of the following techniques: aminoplast crosslinking with residual hydroxy present on extended acrylated or UV cure polymers; oxidative crosslinking of backbone drying oil unsaturation following UV cure; or by employing UV chain extension via reaction of pendent allylic group with polymercaptans followed by a melamine heat cure. The coatings are cured by UV exposure followed by heating or air drying.

We claim: 
     
       1. A coating composition comprising: a first resin containing plural beta hydroxyl alkyl acrylate groups;   a second resin consisting of an aminoplast resin;   a photopolymerization initiator for said first resin, said initiator being selected from those initiators which decompose upon exposure to UV radiation to generate an acid catalyst for the cross-linking reaction of said aminoplast resin and the hydroxy groups of said first resin.   
     
     
       2. The composition set forth in claim 1 wherein said first resin is selected from the group consisting of polyester extended epoxy acrylates, polyester extended urethane acrylates, alkyd extended epoxy acrylates, alkyd extended urethane acrylates and mixtures thereof. 
     
     
       3. The composition set forth in either claim 1 or claim 2 wherein said composition further includes an acrylate group containing monomer copolymerizable with said first resin and a high boiling solvent for said composition, said solvent having hydroxy functionality. 
     
     
       4. A method of curing the coating composition of claim 1, comprising exposing the composition to ultraviolet radiation and subsequently heating the composition to react the aminoplast resin with the ultraviolet cured composition. 
     
     
       5. A method of curing the coating composition of claim 2 comprising exposing the composition to ultraviolet radition and subsequently heating the composition to react the aminoplast resin with the ultraviolet cured composition.